No. If you eat a meal before you weight yourself, you might be heavier (which explains that 1/2 lb gain). So 1 or 2 pound gain/lost is not very accurate and you shouldn't be worrying about it at all. Besides, 1 or 2 pound heavier doesn't mean much. People with more muscle are heavier and they are generally more fit.
I would say once a week is good. I weigh myself whenever I'm in the bathroom which is a terrible habit and I know how it hurts when the number is a few digits up. Usually right after you eat you'll be a lb or two more on the scale since you have a full stomach, and in the mornings it might be a lb or two less since you have an empty stomach. I would do it at night, right before bed.